According to the current state of the art regarding dyeing, bleaching, and drying, different machines are used, some of which comprises a nozzle which serves to spray the bath over the fabric, thus causing the latter to circulate in a tube. Another system consists in propelling the fabric by an overflow from the bath, produced by a device mounted at the inlet of the tube in which the fabric is caused to circulate. Processes which have been known since time immemorial include those in which the bath circulates around the pieces of fabric which are held in a fixed position, and those in which the fabric is driven inside baths contained in fixed vats.
The disadvantages of these various processes are well known. First, they require relatively large amounts of bath, on the order of 10 liters per kg of fabric. Second, these machines are very bulky. Finally, they do not comprise any device for drying.